A new drug treatment could improve the lives of children born with the genetic condition cystic fibrosis, and may even allow them to live longer, say researchers involved in a groundbreaking trial.

There are already drugs to alleviate the symptoms of cystic fibrosis, and reduce the clogging of lungs and digestive system that make it hard to breathe. But the new treatment acts to modify the genetic defect that causes around half the cases of the disease, which affects 10,000 children and young people in the UK – including the son of former prime minister Gordon Brown.

The results of the trial, published in the New England Journal of Medicine, showed a combination of two drugs, lumacaftor and ivacaftor, improved the lung function of young patients and reduced their visits to hospital. It also cut the number of courses of hospital antibiotics they had to take after picking up infections, which is common. There was an improvement in their breathing, their weight and their quality of life.

One of the two drugs, ivacaftor, has already been used on its own in children suffering from a genetic mutation that only causes 5% of the disease, with considerable success. The latest trial tackled the commonest genetic defect, which is responsible for half of all cases. They did not expect to get as good a result because in these children, the protein they were targeting was not sitting on the cell membrane but hidden, said Prof Stuart Elborn from the School of Medicine, Dentistry and Biomedical Sciences at Queen’s University Belfast, where part of the international trial was conducted.

The result was not as spectacular but nonetheless, he said, “it is a breakthrough. It confirms that the underlying genetic defect in cystic fibrosis is amenable to treatment and that we can fix it. There are likely to be even more effective combinations of drugs that may come through.

“These treatments are potentially transformative for young people. They still die in their 20s and 30s. Having a potentially disease-modifying therapy is critically important.”

The trial cannot show that the children will live longer, but Elborn and others hope that a reduction in the severity of the disease will have that effect. In the trial of ivacaftor alone against the genetic defect that causes 5% of cases, young people’s lives were changed. “They are so much more able to function normally than they were. They have started families, gone back to work and come off [lung] transplant lists.

My story of having cystic fibrosis and growing older

Read more

“It is not a cure, but it is as remarkable and effective a drug as I have seen in my lifetime.”

However, the cost of the drugs is very high, which may place a question mark over their use. Ivacaftor alone costs $250,000 (£159,000) per patient per year in the USA. The price in the UK has not been revealed, but the Department of Health agreed to fund it for the small group for whom it was effective. The new combination will be scrutinised for cost-effectiveness by Nice, the National Institute for Care and Health Excellence.

“These results open up a new front in the fight against cystic fibrosis and this combination therapy looks set to be an important additional treatment option that could improve the lives of many,” said Janet Allen, director of research and care at the Cystic Fibrosis Trust.

“This therapy is currently being examined by European regulators for use across the UK. If approved, it will fall to the NHS to fund what is expected to be a high-cost drug.

“As this leading edge of science continues to be explored and better understood, we are hopeful that a future of personalised medicines is increasingly within reach.”